What number can go in the blank? 37, 49, __, 63, 78This was on my son's 1st-grade test. We are all stumped.

I too thought this must be an error, but as the other teacher said, first graders are probably expected to only recognize patterns at this point.  So I thought the error might be that 78 should be 75-- that the pattern is raising the first number (in the tens place) one, and raising the second number by two: 37, 49, 51, 63, 75. So the pattern is 3,4,5,6,7 for the tens place, and 7, 9, 11, 13, 15, with the idea that the first graders would mark the rising number in the one's position.

I can understand how the teacher might accidentally write 78 instead of 75, because as the teacher is increasing the one's place, she was probably writing the pattern while thinking the increases in her head, maybe thinking to herself, okay, so 37, up one 4 up two 9, 49, then 5 and 9 up 2, 11, so 51, then 63, and 63, that's 7 and 5, and as she's thinking of going up to 5, she inadvertently adds the 5 and writes 78.